Clamping device for connecting interchangeable scanning drums to the rotary drive of drum scanners

ABSTRACT

Interchangeable scanning drums of drum scanners that are seated at one side for scanning opaque or transparency image originals must be capable of being reliably and quickly connected to the rotatory drive of the scanner unit. Interchangeable drum structures facilitate the attachment of the image originals and allow an economic assembly of scanning drums that, preparatory to the job, can be loaded with image originals simultaneously with the scanning process. According to the Prior Art 874, it was hitherto necessary to design cost-intensive, actively supported work fixtures in order to achieve an adequately stable connection and a dependable, dynamic operation. The present invention avoids this disadvantage with a cost-beneficial design that makes use of centrifugal forces produced by the scanner rotation for the coupling of drum and drive motor flange in combination with toggle lever mechanisms.

BACKGROUND OF THE INVENTION

Interchangeable scanning drums of drum scanners that are seated at oneside for scanning opaque or transparency image originals must be capableof being reliably and quickly connected to the rotatory drive of thescanner unit. Interchangeable drum embodiments facilitate the attachmentof the image originals and allow an economic assembly of scanning drumsthat, preparatory to the job, can be loaded with image originalssimultaneously with the scanning process. According to the Prior Artdisclosed in, among others, European Letters Patent EP 0 279 874, it waspreviously necessary to design cost-intensive, actively supportedcoupling device in order to achieve an adequately stable connection anda dependable, dynamic operation.

SUMMARY OF THE INVENTION

It is an object of the present invention to avoid the above disadvantagewith a cost-beneficial design. The present invention makes use ofcentrifugal forces produced by the scanner rotation for the coupling ofthe drum and the drive motor flange with toggle lever mechanisms.

According to the clamping device system of the invention for aninterchangeable scanning drum seated at one side in a drum scanner forscanning of opaque and transparency image originals for achieving anadequately stable connection and reliable, dynamic operation, a scanningdrum is provided having a mounting flange centrally positioned relativeto an acceptance flange of a drive motor. The mounting flange of thescanning drum is connected to the acceptance flange of the drive motorwith a plurality of clamping devices. Each clamping device is formed ofa tension lever, a connecting rod, and a clamp lever. Each clampingdevice has at least one spring for generating a basic gripping force forinitial fixing and for preventing sliding upon run-up, the basicgripping force being transmitted via the tension lever, the connectingrod, and the clamped lever. Upon rotation of the scanner, centrifugalforce acts upon a toggle lever mechanism in each clamping device formedof the tension lever, the connecting rod, and the clamp lever, so thatthe gripping force of the clamp lever against the collar of the drumflange is greatly increased in a simple way in order to generate astable and reliable coupling of the mounting and acceptance flanges,despite a tilting force produced by a residual imbalance. Only a slightrelease switch force is provided for a drum change due to the low basicgripping force.

The invention is explained in greater detail below with reference toFIGS. 1, 2, 3 and 4.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the schematic diagram of a drum scanner;

FIG. 2 shows a schematic diagram of a clamping device;

FIGS. 3A and 3B illustrate a structural embodiment of a clamping devicein a side view and in a perspective view, respectfully; and

FIG. 4 illustrates a perspective sectional view of the installationenvironment of the clamping device according to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 demonstrates the principle of a drum scanner with a vertical drumaxis. A scanning drum 1 seated at one side is formed of glass in orderto be able to scan transparent image material with transmitted light inaddition to opaque image material. The scanning drum is held in a metalflange 2 and rests together with this metal flange on the motor flange(5), which forms a unit with the drive motor 6. Metal flange (2) andmotor flange (5) are coupled by three clamping devices arranged offsetby 120° at the circumference that are accommodated in the motor flangeand detailed in FIG. 2. One of the clamping devices is indicated with acircle 3. During a scanning event, the drum (1) rotates and illuminationarm (7) and scanner unit 8—rigidly coupled to one another—move parallelto the drum axis in the drive motor 6 direction. An image originalmounted on the drum surface is thereby resolved into scan lines by thelight beam 9. At the end of the scanning, the illumination arm 7 hasentered into a hollow shaft of the motor flange 5 and the drive motor 6.

FIG. 2 outlines how a centrifugal force 41 in interaction with anextremely slight, static spring power 42 is used for generating adesired gripping force 43. The motor flange 4 carries the structuralelements of the clamping device. Its base is formed by a foot 34. Atension lever 31 is connected thereto via a shaft 35. A connecting rod37 with axial connections 36 and 38 enables the force transmission fromthe tension lever 31 onto a clamp lever 39. The clamp lever 39, like thetension lever 31, is connected to the foot 34 via an axial connection40. A tension spring 33 a already ensures a basic gripping force 43 forfixing the metal flange of the scanning drum 2 on the motor flange 4when the drum stands still. It is structurally insured that the drumtension can only be released by a release force 44 via a release finger32 when the drum stands still. Given rotation of the scanning drum 1with its flange 2 as well as of the drive motor 6 with its flange 5around the axis 5, the centrifugal force 41 is added to the staticspring force 42 and intensifies the gripping force 43.

FIGS. 3A and 3B show a structural embodiment of the clamping device 3 ina side view and perspective view, respectfully. In this embodiment, morebeneficial positions of the axial connections and a torsion spring 33 binstead of the tension spring 33 a were selected. The other structuralelements known from FIG. 2, such as foot 34 tension lever 31 connectingrod 37 clamp lever 39 and the axial connections 35, 36, 38 and 40 servethe purposes described above with respect to FIG. 2. In a perspectivesectional view, FIG. 4 demonstrates the installed position of the clampdevice shown in FIG. 3. The left half of the Figure thereby shows thereleased, untensed condition and the right half of the Figure shows thetension or clamping condition. The glass scanning drum 1 with flange 2motor flange 4 two of the total of three work fixtures 3 arranged offsetby 120° in the circumferential direction, and the head part of theillumination arm 7 via which the release finger 32 is actuated can beseen. In another structural embodiment, a release circuit could actproceeding from the outer circumferential surface of the motor flange 4instead of from the inside through a hollow shaft. Slight spring forcedsuffice for an initial fixing of the scanning drum and for preventing itfrom sliding upon run-up, which means that only a slight switch forcefor changing drums is advantageously required when the drum standsstill. In addition to an extremely small, unavoidable residualimbalance, original scan images that can never be mounted on the drumsurface completely uniformly distributed also effect high tilting forcesgiven the standard, high scanner speeds of approximately 2000 min˜1.Gripping forces that are up to these imbalance conditions can begenerated in a simple way with low expense by the described utilizationof the centrifugal force. The operational dependability would bemaintained given potential spring failures. The invention can berealized both for vertical as well as for horizontal rotationalattitudes of the scanning drum. A retainer hook according to theinitially cited Letters Patent can be utilized for the horizontalrotational attitude for the absorption of the tilting moment in the drumcoupling.

Although various minor changes and modifications might be proposed bythose skilled in the art, it will be understood that my wish is toinclude within the claims of the patent warranted hereon all suchchanges and modifications as reasonably come within my contribution tothe art.

I claim:
 1. A clamping device system for an interchangeable scanningdrum seated at one side in a drum scanner for scanning of opaque ortransparency image originals for achieving an adequate stable connectionand reliable, dynamic operation, comprising: a scanning drum having amounting flange centrally positioned relative to an acceptance flange ofa drive motor, the mounting flange of the scanning drum being connectedto the acceptance flange of the drive motor with a plurality of clampingdevices, each clamping device being formed of a tension lever, aconnecting rod, and a clamp lever; each clamping device having at leastone spring for generating a basic gripping force for initial fixing andfor preventing sliding upon run-up rotation of the scanning drum, thebasic gripping force being transmitted via said tension lever, saidconnecting rod, and said clamp lever; each said clamping device beingdesigned such that upon rotation of the scanner, centrifugal force isacted on a toggle lever mechanism formed of said tension lever, saidconnecting rod, and said clamp lever such that the gripping force of theclamp lever against the mounting flange of the scanning drum is greatlyincreased in a simple way in order to generate a stable and reliablecoupling between the mounting flange of the scanning drum and theacceptance flange of the drive motor despite tilting forces produced byresidual imbalances; and said at least one spring in each couplingdevice being designed such that only a relatively slight release switchforce is necessary for a drum change due to said basic gripping forcebeing relatively low in absence of centrifugal forces generated uponrotation of the scanning drum.
 2. The clamping device system accordingto claim 1 wherein a rotational axis of the scanning drum runsvertically.
 3. The clamping device system according to claim 1 wherein arotational axis of the scanning drum runs horizontally.
 4. The clampingdevice system according to claim 1 wherein three of said clampingdevices are circumferentially spaced around an inside of the scanningdrum at equal circumferential spacings.
 5. The clamping device systemaccording to claim 1 wherein each clamping device has a member foractuating the tension lever for relieving the basic gripping force frominside of the scanning drum.
 6. The clamping device system according toclaim 5 wherein the tension lever is activated for releasing the basicgripping force from an inside of the scanning drum through a hollowshaft.
 7. The clamping device system according to claim 5 wherein thetension lever is activated to release the basic gripping force throughan outside wall of the motor flange.
 8. The clamping device systemaccording to claim 1 wherein a release finger is provided as anextension of said tension lever for application of said release force tosaid tension lever to release said basic gripping force of said clamplever.
 9. A scanning drum system, comprising: an interchangeablescanning drum seated at one side in a drum scanner for scanning of imageoriginals, the scanning drum having a mounting flange abutting anacceptance flange of a drive motor and held in abutting position by atleast one clamping device, the clamping device being formed of a tensionlever connected to a clamp lever; the clamping device having at leastone spring for generating a basic gripping force for initial fixing andfor preventing sliding during initial run-up rotation of the scanningdrum, the basic gripping force being transmitted via said clamp lever;said clamping device being designed such that upon rotation of thescanner, centrifugal force acts on said tension lever such that thegripping force of the clamp lever against the mounting flange of thescanning drum is greatly increased in order to generate a stable andreliable coupling between the mounting flange of the scanning drum andthe acceptance flange of the drive motor; and said tension lever havinga portion for receiving a release force for overcoming said basicgripping force so as to release said clamp lever from said scanning drummounting flange for a drum change.